Oil and natural gas produced from federal leases generated over $6.5 billion in royalties in 2009. To verify that royalties are paid on the correct volumes of oil and gas, the Department of the Interior (Interior) verifies the quantity and quality of oil and gas, both onshore and offshore. This report assesses: (1) the extent to which Interior's production verification regulations and policies provide reasonable assurance that oil and gas are accurately measured; (2) the extent to which Interior's offshore and onshore production accountability inspection programs consistently set and meet program goals and address key factors affecting measurement accuracy; and (3) Interior's management of its production verification programs. Charts and tables.